Problem Description

Given an integer array nums of length n, you want to create an array ans of length 2n where ans[i] == nums[i] and ans[i + n] == nums[i] for 0 <= i < n (0-indexed). Specifically, ans is the concatenation of two nums arrays. Return the array ans.

Approach

Single-Pass Construction.

Solution

class Solution {
    public int[] getConcatenation(int[] nums) {
        int n = nums.length;
        int[] ans = new int[2*n];
        for(int i=0;i<n;i++){
            ans[i] = nums[i];
            ans[n+i] = nums[i];
        }
        return ans;
    }
}